Mobile communication systems were developed to provide the subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services beyond the early voice-oriented services. However, the limited resource and user requirements for higher speed services in the current mobile communication system spur the evolution to more advanced mobile communication systems.
As one of the next-generation mobile communication systems to meet such requirements, standardization for a Long Term Evolution-Advanced (LTE-A) system is underway in the 3rd Generation Partnership Project (3GPP). LTE-A is a technology designed to provide high speed packet-based communication of up to 1 Gbps.
In such a wireless communication system, the UE in the connected mode is allocated radio resource for data communication and, when the data communication is complete, releases the radio resource to enter the idle mode. The UE in the idle mode performs signaling to be allocated radio resource for data communication again.
Meanwhile, with the popularization of smartphone, it occurs frequently that multiple applications are running simultaneously. This causes the UE to generate small data such as keepalive and state transition messages frequently.
In this case, the UE also has to transmit signals to request for allocation and release of the radio resource and core network resource for data communication, resulting in signaling overload of the network.
FIG. 1 is a diagram illustrating the network architecture of an Evolved Packet Core (EPC) network to which the present invention is applied. In FIG. 1, only the entities related to the present invention are depicted among the entities constituting the EPC. The EPS may include other entities responsible for supplementary functions not dealt with herein.
Referring to FIG. 1, the User Equipment (UE) 100 denotes a terminal, and evolved Node B (eNB) 102 denotes an entity of controlling radio resource to which the UE connects through a radio channel.
The Mobility Management Entity (MME) manages the UE 100 in the idle mode and is responsible for the functions related to roaming and authentication of the UE 100. The MME 108 also processes the bearer signal generated by the UE 100.
The Home Subscriber Server (HSS) stores UE-specific subscriber information which is provided to the MME 108 for use in controlling the UE 100 when the UE 100 connects to the network.
The Serving Gateway (SGW) 104 manages user the user bearer of the UE and notifies the MME of the arrival of data addressed to the UE. The PGW 106 delivers data from a service network to the UE or from the UE to the service network. The PGW 106 has a policy for processing the data.
In the EPS, the UE establishes a radio bearer with the eNB for data communication, and the eNB and MME perform context setup and establish S1 connection therebetween.
If a predetermined condition is fulfilled after completing data communication, the MME or eNB performs eNB context release, i.e. releases the S1 connection. The eNB also performs RRC Connection Release such that the UE transitions to the idle mode.
In the case that the UE communicates small data frequently, however, the UE has to transition between the connected mode and the idle mode frequently and thus the network perform S1 connection and data bearer establishment repeatedly, resulting in increase of traffic load.
There is therefore a need of minimizing the number of state transitions of the UE and, in order to achieve this, it is effective to make the UE stay longer in the connected mode. That is, in order to process the small data occurring in the state of no other data communication, the network controls the UE to stay in the connected mode.
However, if the UE stay long in the connected mode, this is likely to cause handover overload.